Overview

Brief Summary

Biology

Darwin's fox is omnivorous and highly opportunistic, having a broad diet including a variety of small mammals, birds, reptiles, amphibians, beetles, invertebrates, fruits, berries and seeds (2) (4). This variable diet is important for the fox's survival as the availability of food items changes with the seasons within its highly fluctuating environment. Although hunting is ordinarily performed alone, up to four individuals may concentrate around a carcass for a few days. On Chiloé, these foxes also sometimes kill poultry and raid garbage dumps, and even enter houses at night in search of food, apparently unafraid of the people and dogs within (2). Whereas this species is primarily solitary on Chiloé, except during the breeding season when temporary pairs form, pairs appear to persist throughout the year on the mainland. These pairs have been known to share their home range with offspring from previous years, with all family members associating closely with one another. Litter size is estimated to be two to three pups (2).

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Description

Discovered by Charles Darwin during his voyage aboard the Beagle (3), Darwin's fox is one of the smallest fox species in the world, with a stout frame, elongated body and short legs (2). The muzzle is small and thin and extends into a rather rounded forehead, and the tail is relatively short and bushy (2). The thick coat is a dark grizzled grey to almost black colour, with a distinctive rusty-red colour on the lower legs and around the ears (2) (4). The abdomen, chest, underside of the muzzle and the inside of the ears are a pale cream to white colour (4), and the tail is dark grey (2).

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Distribution

Range Description

Darwin's Fox is endemic to Chile. It has a disjunct distribution with two populations: one found in the forests of Chilo Island (42S, 74W), and another on the coastal mountains in Nahuelbuta National Park of mainland Chile (3745'S, 7300'W).

Vila et al. (2004) found evidence for what may be a third population at Punta Chanchan, north of Valdivia.

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Darwin's foxes, Lycalopex fulvipes, are endemic to Chile and were once thought only to inhabit Chiloe Island, which is located off the southern coast. The island is over 200 km long and about 30 km west of Chile. Darwin’s foxes are found on most of the island, except in areas to the north where the island is populated by humans. In the 1970’s a mainland population was discovered at Nahuelbuta National Park in Chile (Medel et al., 1990). The park is about 600 km north of Chiloe Island.

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Range

Endemic to Chile, Darwin's fox has a disjunct distribution with just two populations; a small population exists in the coastal mountains in and around Nahuelbuta National Park on the mainland, and a larger population is found about 600 kilometres south on the Island of Chiloé, southern Chile (1) (2).

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Physical Description

Morphology

Darwin’s foxes are characterized by their short legs, elongated body, and short and bushy tails. Their pelage is a mixture of black and grey hair with rufescent markings on the ears and along the lower portion of the legs. White or light markings can be found under the chin and along the underbelly. There are no significant data supporting sexual dimorphism. However, in a comparison done by Jimenez (2006), males did have a larger separation between the upper canines leading to the appearance of a broader muzzle. Dental formula is 3/3-1/1-4/4-2/3 = 42 (Jimenez and McMahon, 2004).

The following average measurements are from unpublished data from J. E. Jimenez of Chiloe Island and C. McMahon of Nahuelbuta National Park and Chiloe Island that were provided in their report for the IUCN/SSC Canid Specialist Group (2004):

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Ecology

Habitat

Habitat and Ecology

Darwin's Fox is generally believed to be a forest obligate species found only in southern temperate rainforests (Jaksic et al. 1990; Medel et al. 1990). Recent research on Chilo, based on trapping and telemetry data on a disturbance gradient, indicates that, in decreasing order, foxes use old-growth forest followed by secondary forest followed by pastures and openings (Jimnez 2000). Although variable among individuals, about 70% of their home ranges comprised old-growth forest. However, compared with the amount available, foxes preferred secondary forest and avoided old growth. Selection of openings varied among individuals. The forest is of Valdivian type, comprising a few native conifers and several species of broad-leaved evergreen species, and dominated by fruit-bearing trees of the Mirtaceae family. This forest is dense, with different strata and very moist all year round (Jimnez et al. 1990).On the Pacific coast of Chilo, Darwin's Fox lives in a fragmented environment of coastal sand dunes mixed with dense evergreen forest. On the northern part of the island, Darwin's Fox uses a relatively flat, but fragmented landscape of broad-leaf forest and dairy cow pastures. Research on the mainland population supports the notion of the species using primarily dense forest (Jaksic et al. 1990; Jimnez et al. 1990). Capture and telemetry data indicate that animals are found in dense Araucaria-Nothofagus forest, open Nothofagus forest and open pasture with decreasing frequency (McMahon et al. 1999). The forest comprises mainly monkey-puzzle trees (Araucaria araucania) and five species of southern beech (Nothofagus spp.), one of which is non-deciduous.

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Darwin’s foxes prefer secondary forest to old growth in areas typical to temperate rainforest vegetation. On Chiloe Island the forest is of Valdivian type. It contains conifer species, a few evergreen species, and fruit-bearing trees. The northern and eastern areas of the island are inhabited by humans and agriculture has had some impact on the landscape. On the west coast of the island, the fox actively uses an evergreen forest habitat fragmented by sand dunes. The mainland population is found in dense forest containing monkey-puzzle trees (Araucaria araucaria) and five species of beech (Jimenez and McMahon, 2004).

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On the Pacific coast of Chiloé, Darwin's fox is found in a fragmented environment of coastal sand dunes mixed with dense, evergreen forest, whereas, on the northern part of the island, the fox uses a relatively flat but fragmented landscape of broad-leaf forest and dairy cow pastures. Preferred habitat is old-growth forest, although secondary forest and pastures and openings are also utilised (1).

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Trophic Strategy

Darwin’s foxes are omnivorous and opportunistic. Their diet varies seasonally with food availability. Their diet contains a variety of food items including small mammals, birds, reptiles, insects, fruits, and seeds. Data from scat analysis show that insects are the most abundant food item but that small mammals make up the largest amount of biomass in the diet. Although Darwin’s foxes may congregate at the site of a carcass, they are mainly solitary hunters. In areas where South American gray foxes (Lycalopex griseus) are present, Darwin’s foxes are more active at night, when South American gray foxes are less active.

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Possible predators of the mainland population of Darwin foxes are pumas (Puma concolor). Large raptors may also prey on these foxes, especially young foxes. However, predation on Darwin foxes has not been described in the literature.

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Life History and Behavior

Behavior

No information on communication within this species has been published. Like other canids, however, they are likely to use olfactory cues, vocalizations, and postural communication extensively. Canids in general have keen senses of smell, hearing, and touch.

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Reproduction

Some evidence suggests that Darwin's foxes are monogamous (Jimenez, 2006). Not much is known about the mating behaviors of this species.

Mating System: monogamous

Breeding season begins in October and pups have been documented leaving the den in December. Based on observations of dens, estimated litter size is 2 to 3 individuals (Jimenez and McMahon, 2004). Weaning takes place in February. Most inferences concerning breeding time come from observations on lactating females caught during trapping of island and mainland populations.

Darwin's foxes show biparental care and the offspring share their parent’s home range for an undetermined amount of time. Parents share their ranges with offspring from previous litters but no observations so far suggest that these offspring contribute as helpers.

Darwin's Fox is endemic to Chile. It has a disjunct distribution with two subpopulations: the species occurs on most of Chilo Island (about 200km long x 62km wide), especially where forest remains, with the exception of the most populated areas on the eastern and north-eastern parts; on mainland Chile, a small subpopulation has been observed since 1975 in Nahuelbuta National Park. It appears that Darwin's Foxes are restricted to the park and the native forest surrounding the park. This park, only 68.3 km in size, is a small habitat island of highland forest surrounded by degraded farmlands and plantations of exotic trees. This subpopulation is located about 600km north of the island population and, to date, no other subpopulations have been found in the remaining forest in between.

Total population size is less than 250 mature individuals with at least 90% of the population occurring in one subpopulation (Chilo Island). Although the species is protected in Nahuelbuta National Park, substantial mortality sources exist when foxes move to lower, unprotected private areas in search of milder conditions during the winter. Some foxes even breed in these areas. The presence of dogs in the park may be the greatest conservation threat in the form of potential vectors of disease or direct attack. On Chilo Island, Chilo National Park has a sizable fox population; however, foxes also live in the surrounding areas, where substantial forest cover remains. These latter areas are vulnerable and continuously subjected to logging, forest fragmentation, and poaching by locals. In addition, being naive towards people places the foxes at risk when in contact with humans. If current relaxed attitudes continue in Nahuelbuta National Park, Chilo National Park may be the only long-term safe area for the Darwin's Fox.

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Most recent estimates place total population sizes at less than 100 individuals in the mainland population and approximately 500 individuals in the island population (Jimenez and McMahon, 2004). The size of the mainland population has been estimated to be on the rise, possibly due to a decrease in number of South American gray foxes (Lycalopex griseus) in the area (Jaksic et al., 1990). A study done by Jimenez (cited by Jimenez and McMahon, 2004) calculated the ecological density of a coastal population on Chiloe Island to be 0.92 foxes km2. This high density was attributed to the large overlap in the territories of these foxes. Agriculture plays a role in limiting the range of Darwin’s foxes in the island and mainland populations. Deforestation rates are limiting the range of these foxes, especially on the mainland where Nahuelbuta National Park is surrounded by agriculture and degraded habitat. On the island these foxes show little to no fear of humans and reports of foxes getting into houses to search for food are not uncommon. Domestic dogs may also present a problem in spreading disease to fox populations (Jimenez and McMahon, 2004).

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Trends

Population

There are few records for the species. Charles Darwin collected the first specimen in 1834 from the south-eastern end of Chilo Island. Osgood (1943) later captured it at the mouth of the Inio River, on the southern shore of the same island. On the Pacific shore of Chilo, the species has been trapped on Playa Tricolor (in June 1999, J.E. Jimnez, pers. obs.) and intensively monitored since November 2001 at Ahuenco; on the Cordillera del Piuch, the fox has been monitored since 1989 (Jimnez et al. 1990). On the northern part of Chilo Island, one fox was captured in November 1999 and at Tepuhueico, on the central part, two adults were observed in June 2002 (J.E. Jimnez, pers. obs.). On the north-western part of the same island, a local recently killed a female and her two cubs; and there have been additional sightings in the same area (C. Muoz pers. comm.). Thus, Darwin's Fox occurs on most of Chilo Island (about 200 km long x 62 km wide), especially where forest remains, with the exception of the most populated areas on the eastern and north-eastern parts.

On mainland Chile, Jaime Jimnez has observed a small population since 1975 in Nahuelbuta National Park; this population was first reported to science in the early 1990s (Medel et al. 1990). It appears that Darwin's Foxes are restricted to the park and the native forest surrounding the park (McMahon et al. 1999). This park, only 68.3 km in size, is a small habitat island of highland forest surrounded by degraded farmlands and plantations of exotic trees (Greer 1966). This population is located about 600 km north of the island population and, to date, no other populations have been found in the remaining forest in between (W.E. Johnson pers. comm.).

Darwin's Fox was reported to be scarce and restricted to the southern end of Chilo Island (Osgood 1943). The comparison of such older accounts (reporting the scarcity of Darwin's fox), with recent repeated observations, conveys the impression that the Darwin's Fox has increased in abundance, although this might simply be a sampling bias.

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Threats

Although the species is protected in Nahuelbuta National Park, substantial mortality sources exist when foxes move to lower, unprotected private areas in search of milder conditions during the winter. Some foxes even breed in these areas. This is one of the reasons why it is recommended that this park be expanded to secure buffer areas for the foxes that use these unprotected ranges (McMahon et al. 1999).

The presence of dogs in the park may be the greatest conservation threat in the form of potential vectors of disease or direct attack. There is a common practice to have unleashed dogs both on Chilo and in Nahuelbuta; these have been caught within foxes' ranges in the forest. Although dogs are prohibited in the national park, visitors are often allowed in with their dogs that are then let loose in the park. There has been one documented account of a visitor's dog attacking a female fox while she was nursing her two pups (E. McMahon, pers. obs.). In addition, local dogs from the surrounding farms are often brought in by their owners in search of their cattle or while gathering Araucaria seeds in the autumn. Park rangers even maintain dogs within the park, and the park administrator's dog killed a guia in the park. Being relatively naive towards people and their dogs is seen as non-adaptive behaviour in this species' interactions with humans.

The island population appears to be relatively safe by being protected in Chilo National Park. This 430 km protected area encompasses most of the still untouched rainforest of the island. Although the park appears to have a sizable fox population, foxes also live in the surrounding areas, where substantial forest cover remains. These latter areas are vulnerable and continuously subjected to logging, forest fragmentation, and poaching by locals. In addition, being naive towards people places the foxes at risk when in contact with humans. If current relaxed attitudes continue in Nahuelbuta National Park, Chilo National Park may be the only long-term safe area for the Darwin's Fox.

No commercial use. However, captive animals have been kept illegally as pets on Chilo Island (Jimnez, pers. obs).

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Darwin's fox is considered critically endangered, being highly vulnerable to extinction due to its small numbers and very restricted range, having just two known populations (4). The greatest threat to this species' survival on the mainland is probably the presence of unleashed dogs in Nahuelbuta National Park, which may attack the foxes and also have the potential to transmit diseases. Despite dogs being prohibited from the park, they are often allowed in with visitors, and subsequently let loose (1). Many foxes have become habituated to humans through unrestricted feeding by visitors, and spend much of their time under vehicles in the car park where they are at risk of being killed by visitors' cars (2). The larger island population appears relatively safer, with Chiloé National Park encompassing most of the still untouched rainforest of the island and containing a sizeable fox population. However, surrounding areas also containing foxes are suffering from ongoing logging, forest fragmentation and poaching by locals (1). Some foxes have been persecuted by farmers on the island for killing their poultry, and attacks from dogs also pose a threat here (2).

The Temuco Zoo held a male and a female until their release in October 2000 on Chilo. No known specimens are kept elsewhere.

Gaps in KnowledgeA high priority would be to conduct intensive searches for other populations between Nahuelbuta and Chilo. There are many remote pockets that are little explored where isolated populations could still be found.

The behavioural ecology of a forest-specialist or forest-dependent species is of utmost interest. Research topics to be explored include: social behaviour (e.g., tolerance to conspecifics), large home range overlaps, presence of helpers, and small litter sizes. In addition, little is known as concerns population dynamics, dispersal behaviour, and metapopulation structure.

Genetic aspects, including levels of inbreeding and inbreeding depression, and past population bottlenecks, are little known and important for future management.

Impacts of and resilience to human-related disturbances, the effects of free-ranging dogs, the foxes ecological naivet to people, and forest disappearance and fragmentation are all of interest for fox survival. The impact of habitat loss (through forest conversion) on fox populations is also of interest. At least in Chilo, habitat disturbance per se seems to play little, if any, role in population dynamics. On the mainland, however, fragmentation might increase risk of predation by other native predators.

Considering the potential disease threat posed by domestic dogs, an investigation into diseases and pathogens (and other allied mortality causes) is crucial.

If Darwin's Fox is so closely related to the Sechuran Fox of southern Peru as the circumstantial evidence suggests, then how did the two species diverge and became separated? These two ranges have been separated by the Atacama Desert for a long time. Exploring this question, in connection with other puzzling biogeographical patterns, could provide evidence to better understand canid speciation and species interactions.

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Conservation

Darwin's fox has been protected by Chilean law since 1929, but enforcement can be difficult, and some poaching unfortunately continues (1). Research and monitoring of this species is ongoing, being undertaken by initiatives such as Darwin's Fox Research and Conservation Project, which also seeks to raise awareness amongst schools, dog owners, farmers and loggers of the plight of the fox and the dangers that imperil it (5). The 430 square kilometre Chiloé National Park protects much of the island population, and the smaller 68 square kilometre Nahuelbuta National Park protects the mainland population. However, a number of foxes at Nahuelbuta are known to move to lower unprotected areas during the winter in search of milder conditions, where they become more vulnerable to mortality. It has therefore been recommended that the park be expanded to protect the foxes that use these areas (1). However, it is also essential that Park wardens become stricter about enforcing Park rules. Dogs brought in by visitors pose a serious threat, whilst continuous feeding of the foxes has habituated them to humans, and thereby made them ever more vulnerable to the dangers people bring. Indeed, it has been suggested that if current relaxed attitudes continue in Nahuelbuta National Park, Chiloé National Park may become the only long-term safe area for this rare, endemic fox (2).

Contents

Pseudalopex is a South American genus of canine distantly related to wolves and is technically not a fox. When Charles Darwin collected a specimen from San Pedro Island in Chiloé Archipelago in December 1834 during the Beagle survey expedition, he observed that this "fox (of Chiloe, a rare animal) sat on the point & was so absorbed in watching [survey work], that he allowed me to walk behind him & actually kill him with my geological hammer".[6] In the 1839 publication of his Journal and Remarks, Darwin said "This fox, more curious or more scientific, but less wise, than the generality of his brethren, is now mounted in the museum of the Zoological Society." He said it was "an undescribed species",[7] indicating that it was distinct from the species (L. culpaeus and L. griseus) that occur on the mainland. Later, Darwin's fox was classified as a subspecies (Lycalopex griseus fulvipes) of the latter.

Darwin's fox does not interbreed with the other Lycalopex species, only lives in forests, and is smaller and darker-colored than the other species. In 1990 a small population of Darwin's fox was found on the mainland in the forested Nahuelbuta National Park, indicating that the fox was not endemic to the island. According to Yahnke et al., in their 1996 article published in the Journal of the Society for Conservation Biology, analysis of mitochondrial DNA of Darwin's fox and the gray fox showed two patterns, indicating Darwin's fox was a new species, closely related to the Sechuran fox. Also according to Yahnke (1995; et al.1996) the present restricted range is a relic of a much wider former range. Zoologists noted the distinctiveness in the ecological niche, appearance, and behavior of this species. Darwin's fox is differentiated from the gray fox in being darker; having shorter legs; a broader, shorter skull; smaller auditory bullae; a more robust dentition; and a different jaw shape and style of premolar occlusion.

In the late Pleistocene, Chiloé Island was connected to mainland Chile by a land bridge. The land bridge was severed about 15,000 years ago when the sea level rose following the last glaciation.[8] This created two isolated populations of Darwin's fox.

Darwin's fox has a vast diet. In dense forests, where it exists, the foxes hunt for mammals, reptiles, beetles, and invertebrates. Sometimes it selects fruits and berries. Birds and amphibians to a lesser degree are also consumed. It sometimes eats carrion, but it mostly eats live animals and fruit. This makes it mostly an omnivore, sometimes a scavenger.

Darwin's fox is generally believed to be a forest obligate species found only in southern temperate rainforests.[2] They only occur in areas of primary forest on Chiloé and on the mainland. They are most active at twilight and before sunrise.. The population of Chiloé has about 200 individuals, and Nahuelbuta on the mainland contains about 50 individuals. The total population size is about 250 mature individuals with at least 90% of the population occurring in one subspopulation (Chiloé Island). Although the species is protected in Nahuelbuta National Park, substantial mortality sources exist when foxes move to lower, unprotected private areas in search of milder conditions during the winter.[9]

It is believed that there are only 250 Darwin's foxes on Chiloé Island and up to 70 on the mainland, and they are listed as critically endangered by the World Conservation Union.[2] Fragmentation of forest adjacent to the national park and on the island is a concern for their conservation, and feral dogs may pose the greatest threat to their survival by spreading disease or directly attacking. Persecution by people who think that the foxes attack domestic fowls, though they pose little threat, is also a potential problem.